Anti-sticking preforms for blow molded articles

ABSTRACT

A preform for a blow molded container provided a tubular body having inner and an outer surface having a first end open to the inner surface and a second closed end opposite to the first end. The relative dimensions of the ends being such that the closed end is receivable in the open end of a similar preform to nest therein. The open end is provided with a passageway to provide communication with the outside atmosphere to prevent formation of a vacuum and thereby enable disassembly of the nesting preforms.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] Polyethylene terephthalate is a polyester resin useful inpreparing blow molded containers to contain a wide variety of liquids.It is desirable that the bottles have excellent strength and a highdegree of clarity. Typically, such bottles are filled with liquid at alocation remote from the location at which the containers are molded.The molded containers are commonly formed by the reheat-stretch-and-blowprocedure. Tubular preforms closed at one end and open at the oppositeend are injection molded of a suitable grade and formulation of PET.

[0003] The molded containers must be packaged and shipped to thelocation at which they are filled with liquid. The preforms aretypically removed from the injection mold and allowed to cool to ambienttemperature and are later introduced to a blow molding system when thepreforms are first heated to a temperature within the glass-transitionrange of the material, then mechanically stretched in the longitudinaldirection, and finally blow molded to the final container configurationand dimensions. The mechanical stretching and blow molding impartbiaxial molecular orientation to the material of the container body,thereby enhancing the tensile strength of the body wall while reducingits thickness. The finished containers are of a great variety of sizesand configurations. The problems of designing a container from a PETmaterial for a particular purpose presents an extremely wide variety ofconsiderations including not only capacity and aesthetic appeal, buteconomy of material and, importantly, whether the container is to befilled with contents under pressure, as is the case with carbonatedbeverages, or under vacuum, as is the case with hot filled products.

[0004] Once the configuration of the container has been determined, apreform must be designed. Due to the necessity of conserving materialand notwithstanding the ensurance that the material forming thecontainer will be distributed properly in the finished container toensure that it will exhibit resistance to deformation and rupture underall conditions of expected use, preform design has become an exactscience.

[0005] When the PET containers are intended for use in packagingcarbonated beverages subject to internal pressures of three to fouratmospheres, a preform configuration has evolved in which the outerdiameter of the closed end is smaller than the internal diameter of theopen end, whereby one preforming, by way of its open end, receive theclosed end of an adjacent preform. The procedure is referred as nesting.In certain instances when the nesting of two or more preforms occurs,two preforms may be locked together by a vacuum created in the enclosedzone between the outer surface of the inner preform and the contactinginner surface of the outer preform. This condition is an impediment tosafety and efficient handling of preforms. Heretofore, it is necessaryto detect and individually separate nested preforms before damage couldoccur to the preforms or the equipment in which they were beingprocessed.

[0006] 2. Description of the Prior Art

[0007] To eliminate the above problem of nesting, the prior art, asillustrated in the U.S. Pat. No. 5,366,774 to H. M. Pinot et al.discloses a preform which in a well-known manner comprises a generallytubular body formed of synthetic resinous material about a central axis.The body is provided with an inner surface and an outer surfacesurrounding the central axis, a first end open to the inner surface, anda second end opposite to the first end. A narrow body portion is axiallyspaced from the second end. The outer surface of the narrow portion hasa radial dimension slightly smaller than the radial dimension of theinner surface of the wide portion.

[0008] The anti-nesting feature includes an interference means formed onthe inner surface at the wide portion to prevent the narrow portion of asimilar preform from nesting within the wide portion of an adjacentpreform.

[0009] The interference means comprise at least one projectionprotruding radially inwardly from the inner surface at the wide portion,such as in axially extending rib.

[0010] The interference means in the preferred embodiment includes, notone, but a plurality of inwardly protruding projections, such as ribs,spaced circumferentially about the inner surface. Each of theprojections protrudes radially inwardly from the inner surface.

[0011] These inwardly extending ribs militate against the entry of thenarrow portion of a similar preform from nesting within the wide portionof the neck finish of the preform. The configuration of the neck finish,once established, is not altered in the blow molding procedure and iscarried over intact to the finished blown container. The inwardlyextending ribs have no function in the finished container and areconsidered surpluses.

[0012] Another prior art structure designed to prevent nesting ofadjacent preforms is illustrated and described in U.S. Pat. No.5,756,172 to Frank E. Semersky. The patent discloses a preform having agenerally tubular body formed about a central axis and having inner andouter surfaces surrounding the axis, a first end open to the innersurface, a second end opposite to the first end, a wide portion of thetubular body adjacent to the first end, a narrow portion of the tubularbody axially spaced from the second end, the outer surface at the narrowportion being a radial dimension smaller than the radial dimension ofthe inner surface at the wide portion, at least one outwardly extendingprotrusion located along the outer surface at the narrow portion andprotruding radially outward from the outer surface of the narrow portiona radial distance greater than the distance between the radial dimensionof the outer surface of the narrow portion and the radial dimension ofthe inner surface of the wide portion to prevent a narrow portion of asimilar preform from nesting within the wide portion.

[0013] The protrusions, being disposed in that portion of the preformwhich undergoes substantial stretching, tend to disappear and blendinvisibly into the finished blow molded container.

[0014] It is an object of the present invention to produce a preformconstruction which militates against the locking of two preformstogether, yet permits the nesting of the preforms.

[0015] Another object of the invention is to produce a preform of adesign permitting the nesting of two or more adjacent preforms whereinthe surface area contact between two nested preforms is minimized toprevent the creation of a vacuum in the closed area of the nestedpreforms.

[0016] The above as well as other objects of the invention may beachieved by a preform for a blow molded container comprising a generallytubular body formed about a central axis and having inner and outersurfaces surrounding the axis; a first end open to the inner surface, asecond end opposite to and spaced from the first end; a wide portion ofthe tubular body adjacent the first end; a narrow portion of the tubularbody spaced from the second end; the outer surface of the narrow portionhaving a radial dimension smaller than the radial dimension of the innersurface at the wide portion, wherein the improvement comprises:

[0017] at least one interruption in the inner surface at the wideportion and extending axially from the first open end toward the secondend and protruding radially outwardly from the inner surface asufficient amount to provide a passageway between the outer surface ofthe narrow portion of a similar preform and the inner surface of thewide portion to prevent a similar preform from sticking within the wideportion by vacuum.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The above objects and advantages of the invention will becomereadily apparent to those skilled in the art from reading the followingdetailed description of the invention when considered in the light ofthe accompanying drawings, in which:

[0019]FIG. 1 is a perspective view of a preform constructed inaccordance with the present invention;

[0020]FIG. 2 is a side view of the preform constructed in accordancewith the invention, as illustrated in FIG. 1, in a nested relation;

[0021]FIG. 3 is an end view of the preform illustrated in FIG. 2 takenfrom the left hand side thereof;

[0022]FIG. 4 is a perspective view of an alternative preform constructedin accordance with the present invention;

[0023]FIG. 5 is a side view of two preforms constructed in accordancewith the invention, as illustrated in FIG. 4 in a nested relation; and

[0024]FIG. 6 is an end view of the preform illustrated in FIG. 5 takenfrom the left hand side thereof.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0025] Referring to the drawings, and particular to FIGS. 1, 2, and 3,there is shown a preform generally indicated by reference numeral 10 forforming a blow molded container intended for the packaging of contentsunder pressure such as carbonated beverages. The preform 10 haspreferably been injection molded of polyethylene terephthalate and isready to be reheated, stretched, and blow molded into final containerconfigurations by the well-known blow molding procedure.

[0026] The preform 10 comprises a generally tubular body 12 having acentral longitudinally extending axis and having an inner surface 14 andan outer surface 16 surrounding the central axis. A first end 18 of thepreform 10 is open to the inner surface 14. A second end 20 opposite toand spaced from the first or open end 18, is closed in a generallyhemispherical configuration.

[0027] A neck finish, generally represented at 22, is provided adjacentthe open end. The neck finish 22 includes male threads 24 adapted tomate with female threads formed in a conventional closure to be appliedwhen the finished container formed by being blow molded from the preform10 has been filled and the closure received over the open end 18 of thepreform. The neck finish 22 also includes a circumferential flange 26which is used in the handling of the preform and the resulting containeron processing and filling lines. The flange 26 is also useful to theconsumer in pouring from the container, since it assists in affording afirm grip on the neck thereof. The configuration of the neck finish 22and the flange 26 once established in the injection mold, are notaltered in the blow molding procedure, whereby they are structurallycarried over intact to the blown container.

[0028] The remainder of the body 12 of the preform 10 in the embodimentillustrated in FIGS. 1, 2, and 3 includes three passageways 30 whichextend longitudinal in a spaced apart parallel relation on the innersurface 14. The passageways 30 commence at the first end 18 andtypically terminate on the inner surface 14 at a point beyond the flange26. These passageways 30 are in the form of interruptions in the smoothinner surface 14 and will allow the preforms 10 to nest and will preventthe creation of a vacuum in the otherwise closed zone generally definedby the inner surface 14 of one preform 10 and the outer surface 16 ofthe nested preform 10 as illustrated in FIG. 2.

[0029] It will be understood that the vacuum which the present inventioneliminates is caused by the nesting of warm preforms. When thetemperature of particularly the outermost preform decreases, the outerpreform tends to commence shrinking causing the tubular body to decreasein dimensional configuration and cause the inner surface to contact theouter surface of the inner nested preform thereby establishing a zonedefined by the outer surface of the inner preform and the inner surfaceof the outer preform and the line of contact between the preforms. Thepressure of the atmosphere within the defined zone decreases as thetemperature decreases. The resulting vacuum condition causes the nestingpreforms to stick together and thereby interfere with the handlingthereof.

[0030] Since the embodiment of the invention illustrated in FIGS. 1, 2,and 3 provides a continuous communication between the outside atmosphereand the closed zone between the two nested preforms preventing thesticking together of the nested bodies and allowing easy disassemblythereof.

[0031] Another embodiment of the invention is illustrated in FIGS. 4, 5,and 6 wherein structural features which are the same as thoseillustrated in the embodiment illustrated in FIGS. 1, 2, and 3 utilizesimilar reference numerals with a prime (′) designation.

[0032] Referring to FIGS. 4, 5, and 6, there is a preform generallyindicated by reference numeral 10′ for forming a blow molded containerintended for the packaging of contents under pressure such as carbonatedbeverages. The preform 10′ has preferably been injection molded ofpolyethylene therephthalate and is ready to be reheated, stretched, andblow molded into final container configurations by the well known blowmolding procedure.

[0033] The preform 10′ comprises a generally tubular body 12′ having acentral longitudinally exterior axis and having an inner surface 14′ andan outer surface 16′ surrounding the central axis. A first end 18′ ofthe preform 10′ is open to the inner surface 14′. A second end 20′,opposite to and spaced from the first or open end 18′, is closed in agenerally hemispherical configuration.

[0034] A neck finish, generally represented at 22′, is provided adjacentthe open end. The neck finish 22′ includes male threads 24′ adapted tomate with female threads formed in a conventional closure to be appliedwhen the completed container formed by being blow molded from thepreform 10′ has been filled and the closure received over the open end18′ of the preform. The neck finish 22′ also includes a circumferentialflange 26′ which is used in the handling of the preform and theresulting container on processing and filling lines. The flange 26′ isalso useful to the consumer in pouring from the container, since itassists in affording a firm grip on the neck thereof. The configurationof the neck finish 221 and the flange 26′ once established in theinjection mold, are not altered in the blow molding procedure, wherebythey are structurally carried over intact to the blown container.

[0035] The remainder of the body 12′ of the preform 10′ in theembodiment illustrated in FIGS. 4, 5, and 6 include three rib members 32which extend longitudinally in spaced relation and extend radiallyinwardly from the inner surface 14′. The rib members 32 producepassageways which commence at the first end 18′ and typically terminateon the inner surface 14′ at a point beyond the flange 26′. Thesepassageways are in the form of interruptions in the smooth inner surface14′ of one preform 10′ and the outer surface 16′ of the nested preform10′ as illustrated in FIG. 5.

[0036] In each embodiment of the invention it will be appreciated thatthe invention effectively minimizes the surface area contact between twonested preforms; and eliminates the creation of a vacuum in the zonebetween the nested preforms. Also, the invention reduces the forcerequired to separate nested preforms due to the reduction in the surfacearea contact during nesting.

[0037] In accordance with the provisions of the patent statutes, thepresent invention has been described in what is considered to representits preferred embodiment. However, it should be understood that theinvention can be practiced otherwise than as specifically illustratedand described without departing from its spirit or scope.

What is claimed is:
 1. A preform for a blow molded container comprising:a generally tubular body formed about a central axis and having innerand outer surfaces surrounding the axis; a first end open to the innersurface; a second closed end opposite to and spaced from the first end;a wide portion of the tubular body adjacent the first end; a narrowportion of the tubular body spaced from the second end; the outersurface of the narrow portion having a radial dimension smaller than theradial dimension of the inner surface at the wide portion, wherein theimprovement comprises: at least one interruption in the inner surface atthe wide portion and extending axially from the first open end towardthe second end and protruding radially outwardly from the inner surfacea sufficient amount to provide an air passageway between the outersurface of the narrow portion of a similar preform and the inner surfaceof the wide portion to prevent a similar preform from sticking withinthe wide portion by vacuum.
 2. A preform as defined in claim 1, whereinsaid interruption is in the form of a groove.
 3. A preform as defined inclaim 2 wherein said groove is formed to extend axially of said tubularbody
 4. A preform as defined in claim 3 wherein said grooves is formedin the inner surface of said tubular body.
 5. A preform as defined inclaim 1 wherein said interruption is in the number of more than one. 6.A preform as defined in claim 1 wherein said interruption is in thenumber of three.
 7. A preform as defined in claim 1 wherein saidinterruption is in the form of a rib.
 8. A preform as defined in claim 7wherein said rib is formed to extend axially of said tubular body.
 9. Apreform as defined in claim 8 wherein said rib is formed in the innersurface of said tubular body.